[UPDATE: Some offers mentioned below have expired and/or are no longer available on our site. You can view the current offers from our partners in our credit card marketplace. DISCLOSURE: Cards from our partners are mentioned below.]

Welcome to the sixth installment of our Best Credit Cards in America series. This time, we pored over dozens of offers for travel rewards cards to determine which ones give customers the best value. We looked at this category of cards since it's the time of year when they're most likely to be put to good use.

To recap how the selection process works: Winners are chosen by how well each card scores based on a unique, 41-factor formula. The higher the score, the better the card is considered to be. The formula gives each card a "benefits/rewards score" and then subtracts the "costs score."

The formula is especially helpful when it comes to looking at a travel rewards card, since you want a product that is going to earn you points that can be put toward future trips, but also save you time and money while you're away on one.  Let's take a look at what three cards best fit the bill.

The winner

PenFed Premium Travel Rewards from American Express

Why it won:

This travel rewards card pulled away from the pack by pairing a particularly generous rewards program with an equally generous APR scale. In fact, the card's only drawback is that it's only available to PenFed credit union members. But this barrier is easily surmounted since everyone is eligible to join if they make a one-time donation to one of the nonprofit organizations associated with the credit union.

The rewards: Cardholders get five points per dollar on airfare and one point per dollar on all other purchases. PenFed is currently running a sign-on promotion that entitles cardholders to 20,000 bonus points (worth $200 towards a round-trip ticket) if they spend $650 within the first three months of opening the account.  There's no cap on the amount of rewards you can earn. The card also offers complimentary 24-hour concierge and big spenders (upon charging $15,000 annually) can get access to participating airline lounges across the world.

The costs: The card currently features a 9.99% annual percentage rate on purchases, cash advances and balance transfers that is fixed through June 30, 2014. (Prospective cardholders can also try to capitalize on an introductory offer on balance transfers that features a 4.99% APR and no fee on the transfer through June 30, 2012). After that time period elapses, all APRs may go up or down, depending on the prime rate.  The card's penalty APR is 17.99%

There's no annual fee. Cardholders also aren't charged foreign transaction fees. Balance transfers beyond June 30, 2012 will incur a 3% fee.

1^st Runner-up

Capital One VentureOne Rewards

The cost-effective version of Capital One's popular Venture brand took second place, thanks, in part, to some nice introductory offers. It also nets brownie points for flexibility since miles can be put toward all travel purchases, including airfare, hotels and car rentals. Capital One also lets you puts miles toward gift cards, merchandise or cash back.

Why it won 1^st runner up:

The rewards: Cardholders earn 1.25 miles per dollar spent on any purchase. Capital One is currently running a sign-on bonus that entitles cardholders to 10,000 miles once they spend $1,000 in the first three months. There's no cap on earning and rewards can be redeemed at any time.

The costs: The VentureOne squeaked into second with a little help from the 0% intro APR on purchases until February 2014. After that, the APR reverts to between 11.9% and 19.9%, depending on creditworthiness. Balance transfers carry the 11.9% to 19.9% APR, but there is no fee associated with moving the balance. There's also no fee for foreign purchases and no annual fee associated with the card.

2nd Runner-up

Capital One Venture Rewards

The presence of an annual fee and a higher APR caused the high-end rewards version of the Venture card to finish behind its more cost-effective predecessor, but a flexible and generous rewards program makes it a solid choice for frequent fliers.

Why it won 2nd runner-up

The rewards: Cardholders earn two miles per dollar on every purchase. The card features the same sign-on bonus as the VentureOne, which entitles new customers to 10,000 miles if they spend $1,000 in the first three months of the account opening. There's no cap on rewards and they can be used at any time with essentially any travel vendor. Capital One does offer additional redemption options. Venture Rewards cardholders also entitles cardholders to complimentary concierge service, an extended warranty program, travel accident insurance and auto rental insurance.

The costs: The card features a $59 annual fee, but Capital One waives that for the first year.  There's no fee on balance transfers or foreign transactions. In terms of APRs, cards feature 13.9%, 16.9% or 20.9% on purchases and balances, depending on creditworthiness.  It also features a 24.9% APR on cash advances and 29.4% penalty APR.

At publishing time, the Capital One VentureOne Rewards Credit Card and the Capital One Venture Rewards Credit Card are offered through Credit.com product pages and Credit.com is compensated if our users apply for and ultimately sign up for these cards. However, this relationship does not result in any preferential editorial treatment.